Since cubic boron nitride (which may be hereinafter referred to as “cBN”) is the highest hardness substance next to a diamond, it is used for various kinds of cutting tools and the like. Such cBN is generally used as a compound sintered body together with a binder, rather than used alone.
Recently, a work material and cutting conditions have been diversified in terms of applications to a cutting tool, which leads to a high level of demands made for a cutting tool using cBN. Particularly, it is desired to improve wear resistance and breakage resistance.
For example, Japanese Patent Laying-Open No. 2000-044350 (PTD 1) discloses that the crater wear resistance of the cutting tool is improved by using cBN particles having an average grain size of 2 μm or more and 6 μm or less. Japanese Patent Laying-Open No. 2000-044347 (PTD 2) discloses that the breakage resistance of the cutting tool is improved by using cBN particles having an average grain size of 0.01 μm or more and less than 2.0 μm.